Field of the Disclosure
The present disclosure relates to computational material science methods and, more particularly, to methods for obtaining and utilizing tight binding parameters based on a momentum-resolved density of states.
Brief Description of Related Technology
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Modern semiconductor nanodevices, such as field-effect transistors (FETs), systems-in-package (SiP), system-on-chip (SoC), photonic devices, nanomechanical devices, nanoelectromechanical systems, etc., have reached device dimensions in the range of several nanometers. These devices consist of complicated two and three dimensional geometries and are composed of multiple materials. Typically, about 10000 to 10 million atoms are in the active device regions with additional contacts controlling an injection of current.
Along with developments in semiconductor nanodevices, the area of Computational Material Science has experienced rapid growth, which growth has largely been enabled by the development of sophisticated methods of electronic and atomic structure calculations. From an electronic structure perspective, ab initio schemes such as Density Functional Theory (DFT) have enabled highly accurate calculations of the properties of bulk solids and small atomic clusters. However, a major limitation in utilizations of DFT for the simulation of electronic devices at realistic length scales is the poor scaling of current DFT-based methods with system size. Even the so-called “Order-N” DFT approaches scale poorly when used in self-consistent simulations of systems having atom sizes greater than a few thousand atoms. Thus, the accuracy and ab initio nature of DFT calculations is offset by the fact that current DFT-based methods cannot be used to model realistically extended device geometries containing several thousands to a few million atoms.
Semi-Empirical Tight Binding (SETB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices. SETB electronic structure calculations for multi-million atom semiconductor systems, such as quantum dots, single-impurity devices, and disordered SiGe quantum wells, have been successfully utilized to quantitatively explain and predict experimental results. Specifically, in the domain of semiconductor-based nano-electronic transport, SETB basis sets along with Non-Equilibrium Green's Functions (NEGFs) have become the accepted state-of-the-art for quantitative device design.
However, the accuracy of current SETB methods depend critically on careful calibrations of the empirical parameters utilized by the methods. The typical way to determine these SETB parameters is to fit SETB results to experimental band structures. This typical approach to SETB suffers from the following difficulties: (i) parameterizations depends on experimental data that is often not available for new and exotic materials; (ii) SETB basis functions remain unknown, which makes it difficult to predict observables, such as optical matrix elements or charge interaction matrix elements, with high precision.